The present invention relates to an air intake device for an internal combustion engine comprising at least two intake pipes, each pipe being closed by at least one throttle valve, and the throttle valves being interconnected.
An air intake device for an internal combustion engine is disclosed in Fischer, U.S. Pat. No. 6,016,780. This air intake device has a header, which is connected to the cylinders of the internal combustion engine via intake pipes. The intake pipes are closed by a pivoted flap having three blades. Variably effective intake pipe lengths are realized by appropriate switching of the pivoted flap.
Especially in internal combustion engines, reliable closing of the flaps is required to fill the cylinders evenly. Various measures are taken to accomplish this. The flaps can be injection molded directly into the duct in an assembly injection molding process. The flaps can also be provided with rubber sealing lips, or sealing rings can be arranged accordingly. When several flaps are coupled to a common actuator, the coupling member must be carefully adjusted so that the individual flaps open and close uniformly. In many cases, the flaps and their housing are made of metal in a very complex and costly manner to keep the gap on the throttle valves and on all flaps as uniform and/or small as possible.
It is an object of the invention to provide an air intake device which alleviates or overcomes the foregoing difficulties.
Another object of the invention is to provide an air intake device for an internal combustion engine having throttle valves, which ensure an even distribution of the amount of air supplied to the cylinders.
It is also an object of the invention to provide an air intake device which promotes reliable closing of a plurality of flap valves and nevertheless can be economically manufactured.
These and other objects are achieved by the invention as described and claimed hereinafter.
In accordance with one aspect of the invention, the objects are achieved by providing an air intake device for supplying air to an internal combustion engine having at least two intake pipes and at least one throttle valve for closing each intake pipe, wherein the throttle valves are interconnected, and the throttle valves have a soft or deformable structure in at least one area in such a way that uneven distribution of the supplied air is reduced.
In accordance with another aspect of the invention, the objects are achieved by providing an air intake device for an internal combustion engine having at least two intake pipes and at least one throttle valve for closing each intake pipe, wherein the throttle valves are arranged off center on shafts and are interconnected, and wherein the individual shafts are each connected to a control rod via an elastically resilient connecting element provided between the individual shaft and the control rod.
Uneven distribution in the air supply to an internal combustion engine can be caused, for instance, by gaps between valve flaps and associated valve seats that differ from cylinder to cylinder. In the case of multi-cylinder engines where several individual flaps are mounted with individual shafts, the flap positions may differ slightly from cylinder to cylinder. Even deviations in the housing geometry, which in this case may also include the resonator tube geometry, may cause uneven air distribution. If the gaps available to the air that flows into the cylinders differ from cylinder to cylinder for any of the aforementioned reasons, then each cylinder receives a different and undefined amount of fresh air. The consequences of uneven air supply distribution may include high exhaust emissions or rough running of the engine. The invention has the advantage of eliminating this uneven distribution.
In accordance with the present invention, the throttle valves have a defined softness or deformability at some locations, which reduces uneven distribution. This configuration is based on the following reasoning: if one cylinder takes in less air than another, then the pressure pattern behind the throttle valve differs for that cylinder. The cylinder that takes in the least amount of air because it has the smallest gap or opening has the lowest pressure behind the throttle valve. Since the pressure in front of the throttle valve is the same in all cylinders, the pressure difference across the flap is greatest in the cylinders that have the smallest opening. If this pressure difference can be used to deform the flap and enlarge the opening, then this cylinder will take in more air. In an ideal case, uneven distribution will be eliminated.
According to one embodiment of the invention, the flap in its closed position is not perpendicular to the center axis of the resonance tube. When the valve is closed starting from the fully open position, the end position should be attained before a perpendicular orientation is reached. The valve should be as rigid as possible in the area of the shaft and the shaft itself should be torsionally stiff. It is sufficient if the throttle valve has one soft or deformable portion.
According to a further embodiment of the invention, this partial area can be realized in that the blade of the throttle valve which is inclined in flow direction is flexible compared to the other blade.
In an alternative air intake device for an internal combustion engine, the shafts of the throttle valves are arranged off-center. The individual shafts of these throttle valves are connected to a control rod. Between each individual shaft and the control rod, a resiliently elastic connecting element is provided. This element has the task of compensating the uneven distribution of the supplied air; i.e., mobility is provided by the elastic element rather than by a soft throttle valve.
In a further embodiment of the invention, the control rod can be moved in a linear or a rotary motion.
These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or in the drawings, and the individual features each may be implemented in embodiments of the invention either individually or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.